A steam-iron process for producing hydrogen from a gaseous fuel, which is a technology that was commercialized in the early 20th century, produces pure hydrogen through repeated redox using iron as a medium (R. B. Gupta, Hydrogen Fuel, CRC Press, 2009; L. S. Fan, Chemical Looping System for Fossil Energy Conversions, Wiley, 2010).
This technology is one of chemical looping processes in the early stage and does not require a water-gas shift reaction or a process of removing CO2 in comparison to steam-methane reforming for mass production.
The steam-iron process has been developed to use a fixed-bed reactor or a fluidized-bed reactor, and efficiency of the chemical looping process is improved with development of technology regarding oxygen carrier particles using iron (Fe) as a basic substance, so it is used to separate undesired substances from a process exhaust gas.
Recently, rather than burning a mixture of air and fuel in a combustion process for producing power using fossil fuel, a method of burning them in an air-oxidation reaction and a fuel-reduction reaction using particles of a metal such as iron, nickel, and copper as a medium has been used, so an exhaust gas can be naturally separated. Further, this technology has been spotlight with respect to consuming a minimum cost for separating carbon dioxide.
In particular, as disclosed in Patent Documents (U.S. Pat. Nos. 6,572,761, 7,404,942, 7,767,191, 2010/0050654, and 2012/0006158), a chemical looping process that uses a gas fuel (natural gas, synthetic gas, and the like), a solid fuel (coal, coke, biomass, and the like), a liquid fuel, and a furnace exhaust gas as a fuel and that uses a metallic medium such as iron or CaS/CaSO4 as oxygen carrier particles can both produce power using combustion, and separate carbon dioxide and produce hydrogen.
Iron used as oxygen carrier particles used in the documents is inexpensive and a large amount of iron is available for the steel industry, so the cost for obtaining it is low. Nevertheless, iron has a defect of poor activation over a long period of time in repeated redox, so porous oxygen carrier particles based on iron having a large surface area and shift efficiency are used.
Porous oxygen carrier particles have a support therein. Further, when solid fuel such as coal is used, ash, sulfur (S), and nitrogen oxides (NOx) should be separated.
However, those chemical looping processes are usually limited to a process of generating power using combustion, even though they use iron, which is widely used in the steel industry, as a medium.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may include information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.